A tire sidewall contains several different records in one place. The mistake is treating them as a single answer to “Will this tire work on my car?”
The safest reading order starts somewhere else: the vehicle manufacturer’s Tire and Loading Information label and the owner’s manual. NHTSA says those are the references for the recommended tire size and cold inflation pressure. The pressure molded into a tire is a tire limit, not the vehicle-specific setting.
Once you have the vehicle requirements, the sidewall can help you verify four separate things: size, service description, identification, and comparative quality grades.
Decision screen
What each marking establishes and what it does not
| Field | What it establishes | What it cannot establish alone |
|---|---|---|
| Vehicle placard or manual | The vehicle maker’s recommended original tire size, cold pressure, and load information. | A sidewall maximum-pressure marking does not replace the vehicle-specific recommendation. |
| Size designation | Nominal width, aspect ratio, construction type, and rim diameter for a common passenger-tire format. | Matching these characters alone does not prove load, speed, wheel, clearance, or system compatibility. |
| Service description | A numeric load index paired with a letter speed rating. | It is not permission to operate at that speed and does not override the vehicle maker’s requirements. |
| DOT symbol and TIN | The DOT mark certifies conformity to an applicable federal safety standard; the TIN identifies the maker and ends with a manufacture week and year. | The date code is not an expiration date and does not reveal storage, damage, repairs, or current condition. |
| UTQG grades | Controlled-test comparisons for relative treadwear, straight-ahead wet braking traction, and heat resistance. | They are not a mileage warranty, full wet-performance score, road-condition forecast, or complete safety ranking. |
Start with the vehicle, not the tire
NHTSA tells replacement-tire buyers to use the same size as the vehicle’s original tires or another size recommended by the vehicle manufacturer. The Tire and Loading Information label is generally on the driver-side door edge or post; the owner’s manual is the other primary reference.
That order matters because two tires can share the same basic size string while differing in load capability, speed rating, construction details, or intended application. A matching size is one required comparison, not the end of the fitment decision.
The same boundary applies to pressure. Use the vehicle maker’s recommended cold pressure from the placard or manual. Do not inflate a tire to the maximum pressure molded on its sidewall simply because that number is visible.
Read the size as dimensions and construction
A common passenger-tire marking such as P215/65R15 breaks into separate fields:
Pidentifies a passenger-vehicle tire in this example.215is the nominal section width in millimeters.65is the aspect ratio: sidewall height expressed as a percentage of section width.Ridentifies radial construction.15is the wheel or rim diameter code in inches.
This tells you what the marked dimensions mean. It does not confirm that the tire clears the suspension and bodywork, matches the approved wheel, preserves the required load capacity, or works properly with the vehicle’s control systems.
If the placard, manual, tire, and wheel do not agree, or if the vehicle uses different front and rear sizes, stop and verify the complete specification with a qualified tire professional.
Keep the service description attached to the size
The characters that follow the size often form a service description. In an example such as 95H, the number is the load index and the letter is the speed rating.
The load index is a coded measure of how much weight one tire can support under its specified conditions. The speed letter describes a laboratory-rated speed capability. Neither field should be read in isolation.
A higher speed letter is not advice to drive at that speed. NHTSA’s guidance also makes clear that inflation, loading, wear, damage, and operating conditions affect actual tire capability. For replacement decisions, compare the complete vehicle requirement rather than only the first size characters.
Find the DOT mark and the full TIN
Under 49 CFR 574.5, the DOT symbol certifies that the marked tire conforms to an applicable Federal Motor Vehicle Safety Standard. The adjacent Tire Identification Number, or TIN, carries identification information used for safety records and recalls.
For a current new-tire TIN, the first group identifies the manufacturing plant, the middle manufacturer code can identify tire characteristics or the brand-name owner, and the final four numerals are the date code.
Those final four digits encode the manufacture week and year. 2325, for example, means the 23rd week of 2025. NHTSA cautions owners to look on both sidewalls because the full TIN may not be visible on the outward-facing side.
The code establishes when the tire was made. It does not supply a universal expiration date, and it cannot tell you how the tire was stored, whether it was run underinflated, whether it has an internal injury, or whether a repair was performed correctly.
Age and condition are separate questions. NHTSA says tire aging cannot be detected simply by looking, while also advising owners to inspect for cuts, cracks, bulges, irregular wear, pressure loss, noise, or vibration and to follow relevant vehicle- and tire-maker replacement guidance.
Treat UTQG as a bounded comparison
The Uniform Tire Quality Grading system covers three fields on many passenger-car tires:
Treadwear
The treadwear number is a comparative grade from a controlled government-course test. A grade of 300 indicates a lower measured wear rate than a grade of 200 under the test system.
It is not a promise of a particular number of road miles. The regulation explicitly says real results can differ with driving habits, maintenance, roads, and climate.
Traction
Traction grades run from AA through C. They measure straight-ahead wet braking on specified asphalt and concrete test surfaces.
The regulation expressly excludes acceleration, cornering, hydroplaning, and peak-traction characteristics. A traction grade is therefore not a complete wet-grip ranking.
Temperature
Temperature grades run from A through C and describe resistance to heat generation and the ability to dissipate heat on a controlled indoor test wheel.
The temperature grade assumes the tire is properly inflated and not overloaded. It does not cancel the effects of excessive speed, underinflation, or excessive loading.
A practical replacement-tire check
Use this order before treating a candidate tire as a match:
- Record the vehicle placard’s size, cold pressure, and load information.
- Check the owner’s manual for alternate sizes, staggered fitment, rotation restrictions, and model-specific instructions.
- Match the complete size and service description, not only the rim diameter or width.
- Confirm the wheel specification and physical clearance.
- Read the full TIN and date code on both sidewalls.
- Inspect the tire’s current condition and ask about storage and repair history when buying used inventory.
- Use UTQG only for the comparisons its tests actually measure.
When any one of those checks is missing, the sidewall has not finished the fitment decision. It has only supplied part of the evidence.